1. Field of the Invention
This invention relates to a paper machine mesh, in particular a forming mesh.
2. Description of the Related Art
Forming meshes are used in the forming section of a paper machine. During the forming process, a fiber suspension from the headbox of the paper machine is applied to one forming mesh or to two forming meshes (in the case of gap formers). In this case, the forming mesh is to dewater the fiber suspension and is to form a fibrous web, wherein as little cellulose fiber and filler material as possible should be separated from the fiber suspension during the dewatering process.
The quality of the formed fibrous web is co-defined in this case to a great extent by the structure of the surface of the forming mesh facing the fibrous web (paper side). The life of the forming mesh, on the other hand, is greatly influenced by the structure of the surface of the forming mesh facing the paper machine (machine side).
To be able to take account of these in part contradictory requirements, multilayer paper machine meshes with a paper-side fabric layer and a machine-side fabric layer were developed, wherein the two fabric layers are connected to each other by so-called ties.
In the case of multilayer fabrics where the fabric layers are held together by separate ties, meaning by ties which form no integral part of the weave structure of at least the paper-side fabric layer, the tie points often cause depressions on the paper side, resulting in markings on the paper produced on such meshes.
In the case of multilayer fabrics where ties form an integral part of the weave structure, the tie points often provide only little tying strength between the fabric layers in return for as flat a paper side as possible. On the one hand the minimal connection between the fabric layers results on the one hand in a large thickness of the mesh, on the other hand it leads to a relative movement of the two fabric layers to each other during operation of the mesh.
The large thickness causes a high degree of water entrainment. Furthermore, a large mesh thickness increases the resistance to dewatering, which results in a poor dewatering of the paper web, which in turn has a disadvantageous effect in particular for high-speed paper machines because the paper web at the end of the dewatering section has too high a water content.
Through the relative movement of the two fabric layers to each other, the layers are worn down against each other, thus shortening the life of the mesh.
Multilayer forming meshes are known from EP 0 432 413 B1, DE 297 24 238 U1, EP 1 00 197 B1, WO 2004/061211A2 and U.S. 2004/0149342 A1 for example.
What is needed in the art is a paper machine mesh on which the connection between the paper-side and machine-side fabric layers is increased without the flatness of the paper-side fabric layer being negatively influenced.